This invention relates to a process for the production of hydroxyfunctional compounds from polyurethane and/or polyurethane polyurea waste by decomposition of these plastics with an alcohol and subsequent reaction of the alcoholysis products to reduce their content of low molecular weight, sterically unhindered aromatic amines.
The decomposition of plastics produced by the polyisocyanate polyaddition process using alcohols is known in principle. However, the problem with these known decomposition processes is that recovery of useful products, particularly from plastics which have been produced using polyisocyanate mixtures of the diphenyl methane series and aromatic diamine chain extending agents (i.e., polyurethane waste rich in urea groups) remains unsolved.
Glycolyzates of polyurethane or polyurethane polyurea waste containing urea groups are characterized by a relatively high content of low molecular weight, primary aromatic amines, especially sterically unhindered, primary aromatic amines (See, e.g., B. Naber: "Recycling von Polyurethanen (PUR)", Kunststoffrecycling-Tagung der TU Berlin, 01.10.1991).
In some cases, the presence of these amines adversely affects the reusability of the glycolyzates in the isocyanate polyaddition process to a considerable extent. A high content of low molecular primary aromatic amines can adversely affect the processability of the glycolyzates, for example, in reaction injection molding (RIM), due to their high reactivity. This is reflected, for example, in excessively short flow paths (i.e., complicated molds cannot be filled).
A high content of low molecular weight primary aromatic amines, especially sterically unhindered primary aromatic amines, may also disrupt synthesis of the polymer to such an extent that the products obtained show inferior properties (high glass transition temperature, low tensile strength and poor breaking elongation).